Donald Trump announced Tuesday that he’s running for president and vowed to be America’s Mr. Fix It — tackling unemployment, illegal immigration and terrorism.

“I will be the greatest jobs president that God has ever created,” the billionaire declared during a 45-minute red-meat speech at Trump Tower, his company’s Fifth Avenue headquarters.

The mogul, known for his “You’re fired”-style moxie and pugnacious oratory style, took no prisoners, slamming Jeb Bush, President Obama, Hillary Rodham Clinton — and Mexico, for sending criminals across the border.

Taking the stage to Neil Young’s “Rockin’ in the Free World,” Trump painted himself as a political outsider, attacking the entrenched Washington, DC, establishment, which he called “stupid” and beholden to special interests — and asleep at the switch while countries such as China, Japan and Mexico “eat our lunch” in trade deals.

“I’ll bring back our jobs from China, from Mexico, from Japan, from so many places . . . and I’ll bring back our money,” he­ said.

Trump vowed to repeal ObamaCare, and blasted the president’s push for a nuclear deal with Iran as a grave threat to Israel.

He mocked the $5 billion Obama­Care Web site as a “disaster.”

The real-estate developer spoke with scorn of America’s failure to build or maintain its infrastructure, singling out La Guardia Airport as fit for a “Third World” country.

But Trump’s most provocative comments concerned the flood of illegal immigrants coming from Mexico. He slammed that nation as more enemy than friend.

“I will build a great, great wall on our southern border. And I will have Mexico pay for that wall,” he said.

On the national-security front, Trump called the Middle East a disaster.

“Our enemies are getting stronger and we’re getting weaker,” he said, vowing to find a new “General Patton” to defeat ISIS.

Trump decried the US strategy in Syria and Iraq, large parts of which are controlled by the savage terrorist group.

“They just built a hotel in Syria. Can you believe this? They built a hotel. When I have to build a hotel, I pay interest. They don’t have to pay interest, because they took the oil that, when we left Iraq, I said we should’ve taken,” Trump said.

He rapped GOP opponent Jeb Bush for being tongue-tied when asked about the Iraq war initiated by his brother, former President George W. Bush.

When discussing the two inmates who broke out of an upstate prison, Trump said, “Interestingly, it’s named Clinton.”

Trump will put on hold his appearances on his NBC “Celebrity Apprentice” show and his weekly guest appearance on “Fox and Friends” as long as he’s on the campaign trail, said a source close to the candidate.